There is currently insufficient evidence to guide policy makers, or physicians and older patients (age 75 and older) with multiple chronic diseases in the decision making process for colorectal cancer screening (CRC). Colorectal cancer screening has been shown to reduce CRC-specific mortality in randomized trials of adults mostly between the ages of 50-75. Mortality curves in these trials begin to separate after 5 years. This finding has led some experts to hypothesize that in order to have an expected net benefit from screening, participants may need to have life expectancies of 5 years or more. This issue, however, has not been specifically examined in models to determine the actual threshold in which the net benefits exceed harms. The long-term goal of our research is to improve the quality of the decisions about colon cancer screening in older adults. Drawing on our extensive experience in decision aid development, we are developing decision aids for both physicians and patients to inform individual decisions about screening that are tailored to the patient's age, burden of co-morbidities, functional status, risk of complications, and chance of benefiting from screening. In order to develop high-quality decision tools, we require better information about the effects of life expectancy and co-morbidities on the potential benefit of screening. We plan to adapt our existing, well-validated model of colon cancer screening to examine the cost-effectiveness of screening at different age ranges and life expectancies. We will modify the existing model by incorporating advanced ages and different numbers of co-morbid conditions or levels of functional status into the model. Through these adaptations we will accomplish the following specific aims: Aim #1:To test the incremental cost-effectiveness of continuing CRC screening vs. stopping screening in average risk patients ages 70, 75, 80 and 85. Aim #2: To determine the effect of different levels of chronic illnesses, different levels of functional status, and different risks of screening complications on life expectancy and the cost effectiveness of colon cancer screening in older patients. Aim #3: To incorporate the information generated from these models into our existing patient and physician decision aids for use in individual, tailored patient-physician communication and test their usability with physicians and older adults. The next step will be to test the effect of the tailored patient and physician decision aids on decision making outcomes in a randomized control trial.